Odd orchid and funny fern favour the softer tree fern trunk

Back in July, I took a walk with Don Teese and (my) wife Lynda, to see a couple of plants in flower at in the Dandenong Ranges near Melbourne. I'll feature one of those, a tiny orchid, today, and the other, a big tree, next week.

Along with the orchid I'll throw in for nothing a weird fern-like plant that has the same odd habitat preference - the trunks of a tree fern. And not just any tree fern for both of them. Almost always the Soft Tree Fern, Dicksonia antartica (rather than its frequent companion, the Hard Tree Fern, Cyathea australis).

Let's start with the orchid, a Corybas, or Helmet Orchid. You can see in the picture at the top of the post where the name comes from. The flowers are only 5 or so millimetres across (although Neville Walsh says up to one centimetre) so they are easily missed. Typically they flower in winter, in rather damp places, and on the ground.

This particular species, the recently named and described Corybas grumulus, almost exclusively grows on the trunks of the Soft Tree Fern in this location. The Mountain Helmet Orchid is what we would call an epiphyte. In other places it will occupy more normal terrestrial habitats.

There is a similar species that grows on the ground, but it is a bit larger flowered and the 'boss' is a different colour. We call that inflated gullet inside the helmet a 'boss'. In the ground-dwelling species it is mostly white, in this one, a pinkish purple hue (or at least a bit translucent).

Helmet Orchids are pollinated by suitably tiny fungus gnats. They spread (I think) by sending out root-like shoots, called stolons, that form new tubers elsewhere on the trunk. So they don't have to rely entirely on seed landing on the right tree fern at the right time (where like most orchids, they need to meet up with a real fungus - not a gnat - for the seed to germinate).

Growing on the same species of tree fern, but in a different setting, was this odd plant once thought to be a close relative of ferns and now welcomed as a true fern. It's called Tmesipteris obliqua, the Long Forkfern. It's most closely related to a thing called the Skeleton Forkfern, Psilotum, and that too was once considered to be not really a fern... They are grouped in their own family, Psilotaceae.

You can see the spore capsules in this next picture, the pale brown moustache-shaped apparatus on the main stem. Each sits within a something that looks like a typical leaf, but has two lobes. It's called a sporophyll - that is, the leaf around the spores or spore container.

Tmesipteris is only found in Australia, New Zealand and New Caledonia. There are about 20 species, all looking pretty much like this. It does have an 'alternative' phase, a tiny gametophyte, which grows only in close association with a fungus, like the orchid. And for that matter, most plants, although in variously different ways.

The Forkfern is scattered widely across the State, and in New South Wales and Tasmania, where you find this kind of habitat. The orchid seems to be rarer, and is only found in Victoria. Both would have been more common when there was more natural fern gully vegetation, and more soft tree ferns, in the Dandenong Ranges.